7. Anatomy of the breast Flashcards
What is the breast comprised of?
Glandular, fat and fibrous tissue
Describe embryology of the breast
Derived from precursor ectoderm cells during week 4
Form mammary bud by week 5
Background breast stroma develops throughout gestation
>12 weeks, secondary buds lengthen and branch forming a complex network of radially arranged breast ducts that connect the nipple with the mammary lobules
Where does the breast extend from?
Between 2nd and 6th rib spaces, from caudal to cranial
From lateral border of sternum to mid-axillary line
How are breasts split?
Into 4 quadrants
Upper/Lower and Inner/ Outer
Where does the majority os tissue lie compared to the remaining breast?
Upper outer quadrant
How many ductal lobular units are in the breast? Where do they drain?
15-20 ductal-lobular units
Each drains into a main duct
What lies interspersed between ductal lobular units?
Fat
What structures divide the ductal lobular units?
Fibrous septae that radiate from the centre outwards
What holds the breast?
Suspensory ligaments of Cooper (Coopers ligaments)
How many milk ducts are there in the breast?
4-18
Describe the blood supply to the breast
Branches of the: Lateral thoracic artery Internal thoracic artery Thoracoacrominal artery Thoracodorsal artery Intercostal arteries
What are the 3 principle groups of veins draining the breast?
Perforating branches of the internal mammary vein
Tributaries of the axillary vein
Perforating branches of the posterior intercostal veins
Describe the main innervation to the breast
Anterolateral and anteromedial branches of thoracic intercostal nerves T3-T6.
Also innervation from the supraclavicular nerves to the upper and lateral parts of the breast.
Describe innervation to the nipple
Dominant supply from the lateral cutaneous branch of T4.
Where does the predominant lymphatic supply come from?
The axila
What are the 5 groups of axillary lymph nodes?
Humeral Subscapular Pectoral Central Apical
Describe % of drainage of the breast
75% of breast drains to lymphatics in axilla
25% of breast drains to lymphatics in Internal Mammary nodes
Level 1 lymph nodes in pyramidal space
Lateral to pec minor
Level 2 lymph nodes in pyramidal space
Posterior to pec minor
Level 3 lymph nodes in pyramidal space
Medial to pec minor
Lymphatic drainage of breast and axilla
Pyramidal compartment, tightly invested between the upper extremity and thoracic wall, 4 boundaries:
Medially: Serratus Anterior
Laterally: Intertubercular groove of humerus
Anteriorly: Pectoralis Major and Minor
Posteriorly: Teres Major, Subscapularis + Latissimus Dorsi
Why do surgeons have to be careful when extracting lymph nodes?
Long thoracic nerve: damage results in winging of scapula
Thoraco-dorsal pedicle nerve: damage results in reduced power when lifting arm above head
Intercostal brachial nerves: Damage results in loss of sensation to upper inner aspect of arm
Sentinel node biopsy
Mapping procedure.
Remove first 2-4 lymph nodes that drain breast cancer to the axilla.
Breast cancer lymphoedema
Puffy swollen arm, debilitating
Occurs 2-3 years after lymphatics have been removed in surgery.
Lymphoedema
Abnormal, generalized or regional accumulation of protein rich interstitial fluid
Oedema formation and change in tissue architecture
Reduction in lymphatic transport capacity from arm with an increase in lymphatic load
Risk factors for lymphoedema
Axillary surgery Radiotherapy Chemotherapy High BMI Infection/ trauma
Strategies to reduce lymphoedema
Less axillary surgery
Axillary reverse mapping (ARM)
LYMPHA
Axillary reverse mapping
Discriminate lymphatics that drain the arm from the lymphatics that drain the breast
Aims to identify and preserve nodes and/or lymphatics draining from the arm during ALND, thereby minimizing arm lymphedema
Congenital abnormalities affecting breast
Underdevelopment/ absence of 1 breast (may coexist with muscle/ribcage anomaly) = Poland syndrome Accessory nipples (polythelia) Absent nipples (athelia) Accessory breast tissue Tubular breast defomity
